The dry-cell construction Leclanche devised by 1886 affords the basic principle on which the present time dry or primary batteries are constructed. According to Leclanche's construction, a carbon plate or rod was encircled by a mixture of powdered carbon and manganese dioxide, with an amount of 10-20 weight percent ammonium chloride solution. Manganese chloride was sometimes added. As the battery case, zinc sheet was used.
A 1.5 volt changing tension was obtained. From such value the tension slowly dropped off, with an actual average value being from 1.2 to 1.3. During its inactive condition, the original tension was nearly wholly regained, the battery being so particularly useful for intermittent action.
The general chemical reaction involved is now expressed as follows: EQU Zn+2NH.sub.4 Cl+2MnO.sub.2 .fwdarw.Cl.sub.2 Zn.2NH.sub.3 +H.sub.2 O+Mn.sub.2 O.sub.3
Dr. Carl Gassner in 1888 improved the Leclanche cell, originating the first dry-cell battery. The improved battery was comprised of a zinc case, acting as both the battery anode and its container. A gel-like electrolyte was put up within such container and a carbon rod, encircled by depolarizing mixture, was located at the center thereof. This is the basic construction followed at the present for manufacturing commercial dry batteries, of any model, which are currently used to generate low-voltage electric power.
Broadly, the electrolyte heretofore used for dry batteries has consisted of a gel-like body containing therein about 20 weight percent ammonium chloride and 9 weight percent zinc chloride, arranged between the battery anode and cathode. Such gelly paste usually comprises a mixture of the electrolyte substance and corn starch and wheat meal. Synthetic materials affording improved electrical properties and longer shelf life, such as methyl-cellulose, Cellosolve and the like, are also used.
It is well known that during the discharging process the battery electrolyte changes in composition. In the layer adjacent the zinc electrode the pH value changes from about 5.7 to about 3.8 (thus becoming more acidic) while in the innermost region the pH of the mixture changes from about 5.8 to 11 (more alkaline).
Dry batteries comprising the aforecited conventional electrolyte, generally show a steady slow rate characteristic of discharge, until reaching the 1-volt final tension, when discharging at 20.degree. C. The electrical tension of the battery continuously decreases as it discharges. The rated capacity depends upon, therefore, the intended final tension. For comparison purposes, when testing commercial Size D batteries, at a 4 ohms load, the results set forth in the following Table I are obtained, for different final tensions.
TABLE I ______________________________________ Final Time Watts- Voltage hrs. Ah hr. Wh/kg. ______________________________________ 1.4 0 0 0 0 1.2 0.25 0.244 0.317 0.31 1.0 2.35 0.681 0.792 8.27 0.9 3.50 0.955 1.04 10.87 0.8 5.50 0.37 1.37 14.33 ______________________________________
Another kind of electrolyte uses 20 weight percent caustic soda, in which the zinc goes into reaction to form sodium zincate, the hydrogen released being absorbed at the carbon surface by the atmospheric oxygen occluded within the electrolyte, thus spending air at a rate above 1 liter in one hour. In order to decrease the hydroxyl ion consumption, calcium hydroxide, which is scarcely soluble, is added to the electrolyte, thereby forming soluble calcium zincate being so reclaimed the sodium hydroxide. The electrolyte in this latter kind of dry battery is held in place by adding thereto corn starch paste. Preferably, the miniature 5.5 ampere-hour dry batteries are so constructed.
Also, the electrolyte may be comprised of 35-40 weight percent potassium hydroxide saturated with sodium zincate, supported on .alpha.-cellulose.
The aforecited prior art batteries have a rather short life as contrasted to that one attainable in the batteries according to the present invention.